Many aqueous industrial and household cleaners, such as laundry detergents, contain a mixture of enzymes and surfactants. The enzymes can include one or more of a combination of proteases, amylases, lipases, cellulases and pectinases, and serve to attack or degrade organics, such as grease, oil, or other soil, while the surfactant acts to disperse the degraded particles in the aqueous phase. Surfactants contain both hydrophilic and oleophilic groups, and according to the dispersion mechanism, an oleophilic group on the surfactant will attach to a particle of the oil, grease, or other soil, and pull it into dispersion by attraction of the surfactant's hydrophilic group, for the water with which it is added. The dispersion is maintained by the action of the hydrophilic groups in the surfactant. The hydrophilic groups on different surfactant molecules repel each other, which necessarily results in repulsion between the particles of oil, grease and soil.
Cleaning compositions of this type containing enzymes and a surfactant have been used in the past to remove soiled lubricant from industrial machinery by impinging the aqueous cleaning composition on the surface to be treated through high pressure hoses or jets. Compositions of this type have also been used to clean reactors or other vessels by flowing the composition through the vessels by the action of circulating pumps. To clean oil from ships bilges, the composition containing a surfactant and enzymes has been added to the ship's bilge and the rolling motion of the ships will provide agitation to effectively clean oil and other oleophilic materials from the bilge.
Another method of use in the past has been in cleaning trickling filters in waste water treatment systems, in which the surfactant/enzyme solution is dripped into the influent passing over the filters.
A conventional batch coker fractionator, as found in an oil refinery includes, among its ancillaries, fin fan heat exchanger tubes that are connected to the upper end of the fractionator. While the fractionator itself can be cleaned by cascading a cleaning solution containing surfactants and enzymes through the fractionator column, the fin fan exchanger tubes are not included in the cascading system and in the past have been separately cleaned. As the tubes may contain noxious gases, such as hydrogen sulfide, the initial step, as used in the past, has been to pass an alkaline material, such as sodium hydroxide, through the tubes to react with and remove the hydrogen sulfide gas. After the content of these gases has been reduced, the tubes are subjected to a blast of water under high pressure, in an attempt to loosen the scale and coke from the walls of the tubes. The conventional procedure for cleaning the fin fan exchanger tubes of the fractionator normally requires 2 to 3 days, but the procedure has not been shown to be effective in removing all scale and coke buildup within the tubes. Not only has this procedure been relatively ineffective in removing the deposits from the tubes, but due to the extended time required, there is additional substantial down time for the fractionator.